Brush holder construction with dust slots



April 28, 1970 w. s. BRUCKER 3,509,399

BRUSH HOLDER CONSTRUCTION WITH DUST SLOTS Filed Feb. 14. 1968 INVENT OR WILLIAM S. BRUCKER ATTORNEY United States Patent 3,509,399 BRUSH HOLDER CONSTRUCTION WITH DUST SLOTS William S. Brucker, Towson, Md., assignor to The Black and Decker Manufacturing Company, Towson, Md., a corporation of Maryland Filed Feb. 14, 1968, Ser. No. 705,361 Int. Cl. H01r 39/40 US. Cl. 310-242 1 Claim ABSTRACT OF THE DISCLOSURE SUMMARY OF THE INVENTION The present invention deals specifically with the configuration of the brush holder passages in which the carbon brushes slide, which configuration is such as to virtually eliminate any tendency at the brush to stick therein, commonly referred to as brush hang-up. The passages include guide surfaces which slidably guide the brushes but are relieved at their corners along at least a major portion of the holder length and at least to one open end thereof, to prevent accumulation or build-up of contaminant matter on the guide surfaces of the holder passage which otherwise might tend to restrict free advancing movement of the brushes toward the commutator as the brushes Wear.

Main objects of the present invention, therefore, are to provide an improved brush holder construction which prevents the accumulation or build-up of dust, dirt, etc. on the brush guiding surfaces in the brush passage therein and facilitates and insures free movement of the brush Within the passage.

Further objects of the present invention are to provide an improved brush holder construction of the above character which is relatively inexpensive to manufacture, rugged in construction and reliable in use.

Other objects and advantages will become more apparent from a consideration of the detailed description to follow taken together with the drawings annexed hereto.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary view illustrating a typical installation of a brush holder embodying the present invention and shown partly in section and with parts removed for clarity;

FIG. 2 is a perspective view of the brush holder of the present invention and shown partly broken away and with the brush terminal and spring removed for clarity; and

FIG. 3 is a top plan view of FIG. 2 and shown with the brush and terminal in place therein.

BROAD STATEMENT OF THE INVENTION Broadly described, the present invention includes a brush holder comprising an elongated body having a generally polygonal cross-sectional passage therethrough adapted to have a carbon brush disposed therein, said passage defining guide surfaces adapted to slidably and non-rotatably guide said brush, said passage being relieved between each adjacent intersecting pair of guide surfaces along at least a major portion of the length of said body and at least to one end of said passage.

In another aspect, the present invention includes a brush assembly comprising a brush holder having generally polygonal cross-sectional passage therethrough, a brush slidably and non-rotatably disposed in said body passage, means normally biasing said brush toward one end of said passage, and a plurality of slots in said passage extending along a major portion of the length of said body and at least to one end of said passage, one of said slots being at each corner of said passage.

DETAILED DESCRIPTION Referring now more specifically to the drawings, an electric motor embodying the brush holder of the present invention isshown partly in FIG. 1 and indicated at 11 and is seen to include a field 13 fixedly mounted in a motor frame 15. An armature, which includes windings 17, a commutator 19 and a shaft 21, is rotatably supported within the field 13 by means of bearings 23 (only one of which is shown) at either end of the shaft 21 and which are carried by the frame 15. As is conventional in this type of motor, a pair of carbon brushes 25 (only one of which is shown) engage the commutator 19 to interconnect the latter with an electrical source. Each brush 25 is carried by an insulating brush holder 27 (only one of which is shown) which holder, in turn, is carried by the frame 15. The motor frame 15 may be of clam-shell configuration having a recess 29 in one part to receive the brush holder 27. Projections (not shown) on the other motor frame part (not shown) fit into pockets 31 in the brush holder 27 to trap and hold the latter in the recess 29.

The brush 25 is slidably disposed in a through passage 33 in the brush holder 27 and is biased toward one end thereof by a compression spring 35 also dis posed within the passage 33. An electrical lead 37 extends through an elongated slot 39 in one side of the brush holder 27 and has a terminal 38 held against the brush 25 by the spring 35. Preferably, but not necessarily, the terminal 38 has laterally projecting ears 40 which slide in guide slots 42, 44 in the holder 27. The slots 42, 44 terminate in shoulders 46 near the end of the passage 33 which limit the movement of the terminal 38 through the passage 33 as the brush 25 Wears. The other end of the spring 35 bears against a cover 41 which may be secured to the brush holder 27 or carried by the motor frame 15. In addition, the spring 35 may be secured to the terminal 38 in which case the spring serves as a handle to remove the terminal 38 from the passage 33 for inspection of the brush. This construction forms no part of the present invention and is not illustrated nor described further here; however, reference may be made to the co-pending application of David E. Harvey et al., Ser. No. 712,270 filed Mar. 11, 1968 and owned by the assignee of the present application, for a detailed explanation thereof.

During operation of the motor 11, carbon dust is formed as the brush 25 bears against and is worn by the commutator 19. In addition, other dirt, grease, foreign matter, etc. is drawn into and through the motor 11 with the cooling air that moves therethrough. Some of this contaminant material, of course, gets into the brush holders, particularly those which have through passages and/or a lead slot 39 therein such as the brush holder 27 illustrated here. As the brush 25 moves in the brush holder passage 33, it tends to wipe the walls of the passage 33 between the corners and keeps them clean. However, the brush 25 pushes some of this contaminant material into event, contaminant material tends 'to accumulate-and build up in the corners of the passage 33 and eventually can restrict or even prevent free advancement of the brush 25 toward the commutator 19 as the brush 25 wears. This condition, referred to as brush hang-up, is highly undesirable for the reason that it causes poor commutation which can result in damage to the entire motor structure. To alleviate this situation, limited dimensional guide surfaces are provided in the brush holder passage 33 to slidably and non-rotatably guide the brush 25 in advancing toward the commutator 19, and relief areas are provided at least between each intersecting pair of guide surfaces (or at the corners of the passage 33) to. prevent such build-up of contaminant material in the passage 33 as would cause brush hang-up.

Thus, as shown in FIGS. 2 and 3, the passage 33 defines a plurality of guide surfaces 45, 47, 49, 51 which slidably and non-rotatably guide the brush 25. The passage 33 is relieved, as shown at 43, at the intersection between each adjacent pair of surfaces 45, 47, 49, 51, or at each corner of the passage 33. These. reliefs or slots 43 extend at least along a major portion of the length of the brush holder 27 and at least to the inner or open end of the passage 33 through which the brush 25 extends, and preferably the slots 43 extend the full length of the brush holder 27 as shown. The slots 43 or relief areas may be of any suitable or convenient cross-sectional configuration, it being understood that the con figuration shown here is by way of illustration only. A number of brush holders, such as that illustrated here, are, molded using a relatively rigid, insulating material like, for example, a phenolic. In that'case, the relieving slots 43 can be molded directly into the brush holder 27 at little or "no additional cost.

, In use, the brush 25 wipes agalnst the guide surfaces brush 25 so that good commutation throughout the life of. the brush is insured. In addition to the reliefs 43, each of the'guide surfaces 45, 47, 49, 51 is divided, over a major portion of its length by the slots 42,v 44, 39 and a slot 48, respectively. Thus, the area of the surfaces 45,

47, 49, 51, which slidably engage the brush 25, is reduced even further so that even less contaminant material has a chance to accumulate on thebrush guiding surfaces of the passage 33. Furthermore, the relatively open construction provided by the reliefs 43, as well as the slots 42, 44, 48, 39, makes it possible to use the motor cooling air to both assist in removing contaminant material from within the cavity 33 as well as to cool the brush 25 during motor operation. 1

By the foregoing, there has been disclosed an improved brush holder construction calculated to fulfill the inventive objects hereinabove set forth, and while a preferred embodiment of the present invention has been illustrated and described in detail, various additions, substitutions, modifications and omissions may be made thereto without departingfrom thespirit of the invention as encompassed by the appended claim; I claim: 1 1. A brush holder assembly comprising an elongated body having a generally polygonal guideway therethrough from end'to end, a carbon brush slidably guided in said guideway, a spring in said guideway normally biasing said brush toward an end of saidguideway, a s1ot.in one wall of said guideway, an electrical lead extending through'said slot and having a terminal engaging said brush, said terminal adapted to move along said guideway and said lead adapted to. move along said slot under the force of said spring' as said brush wears, abutment means within said guideway preventing withdrwal of said 1 terminal through said one end of said guideway, and a plurality of dust slots formed in said body at the .corners of said guideway and extending to said one end thereof.

. I References Cited MILTON o. HIR-SIE-IIFIELD', Primary Examiner L. L. SMITH, Assistant Examiner US. Cl. X.R. 

